Tag Archives: sea ​​level rise

Comment: Rising sea levels and sinking landmasses are sweeping big cities but the solutions are far from simple | Instant News


NORWICH, UK: It is well known that climate-induced sea level rise is a major threat. What is less known is the threat of sinking the land. And in many of the most densely populated coastal areas, land is sinking faster than sea levels are rising.

Parts of Tokyo for example sank 4m during the 20th century, with 2m or more sinking reported in Shanghai, Bangkok, and New Orleans. This process is known as subsidence.

Slow subsidence occurs naturally in river deltas, and can be accelerated by the withdrawal of groundwater, oil or gas causing the soil to consolidate and the surface to lose altitude.

Land subsidence causes relative sea level rise (sea level rise plus land sinking). It turns out that agricultural land is becoming salty, damaging buildings, causing widespread flooding that can even mean the loss of the entire coastal area.

READ: Singapore’s mean sea level is now 14cm higher than the ‘pre-1970 level’: Met Service

Land subsidence can threaten flooding in low-lying coastal areas, much more than sea level rise, but scientists are only just becoming aware of the global implications of the threat with regard to coastal cities.

In fact, although the average coastal area is experiencing a relative sea level rise of less than 3mm per year, the average coastal population is experiencing an increase of about 8mm to 10mm per year. This is because a lot of people live in the delta and especially the cities in the delta that are receding.


A man drives a rickshaw carrying vegetables and other items through a flooded road in an area affected by land subsidence and rising sea levels in North Jakarta, Indonesia, June 5, 2020. REUTERS / Ajeng Dinar Ulfiana

That’s a key finding from our new study, in which we analyze how rapidly cities are sinking around the world and compare this to global land subsidence data including less densely populated coastlines.

Our findings reflect that people often choose to live in river deltas, floodplains and other areas that are already prone to sinking, and thus further increase land subsidence.

READ: Comments: As the ice sheet melts, Singapore becomes a hot spot for sea level rise

In particular, receding cities host more than 150 million people in the coastal zone – that’s roughly 20 percent of the world’s people who live by the sea. This means that relative sea level rise will have a more sudden and more severe impact than scientists previously thought.

Here are some of the cities most affected:

JAKARTA

The Indonesian capital Jakarta is home to 10 million people, and is built on a lowland next to the sea. The withdrawal of groundwater caused the city to sink more than 3m from 1947 to 2010 and large parts of the city still sink 10cm or more each year.

Land subsidence does not occur evenly, creating uneven risks that make urban planning difficult. Buildings are now flooded, cracks appear in abandoned infrastructure.

Jakarta has built a taller sea wall to compensate for land subsidence. However, as groundwater pumping continues, this patching policy can only last long before the same problem recurs. And cities need to keep pumping because groundwater is used for drinking water. Fetching water, which is essential for human survival, ultimately puts people at risk of waterlogging.

The battle against land subsidence is slowly disappearing, with the government proposing in 2019 to move the capital to a purpose-built city on the island of Borneo more than 1,000 km away, with land subsidence being one of many reasons.

SHANGHAI

Thriving in the last few decades, and now with a population of 26 million, Shanghai is another shit. The city has a maximum subsidence rate of about 2.5 cm per year. Again this is largely due to lowering the groundwater table, in this case thanks to drainage for building skyscrapers, metro lines and highways (eg Metro Line 1, built in the 1990s, led to rapid subsidence).

views of Shanghai, China

More than just a sight to behold, Shanghai is also a city that has successfully blended the old and the new. (Photo: Adrian Tan)

If no additional cover is built, by 2100 this rate of sea level decline and rise means that storm surges could overwhelm about 15 percent of the city.

NEW ORLEANS

In New Orleans, embankments and ditches over the centuries have effectively drained the city and submerged it, leaving about half below sea level.

READ: Comments: Singapore’s climate change battle needs to be clear about these facts

When Hurricane Katrina hit the embankment in 2005, the city didn’t stand a chance. The hurricane caused at least US $ 40 billion in damage and particularly affected the city’s African American community. More than 1,570 people died across the state of Louisiana.

If the city did not recede, the damage would be greatly reduced and lives would be saved.

Decisions made decades or more ago paved the way for the catastrophe seen today, and what we will see in the future.

Tourist Town-Sea Rise

Flood waters covered roads, sidewalks and neighborhood lawns in Ocean City, NJ on October 30, 2020. The city faces the costs of rising sea levels, both in terms of monetary and disruption caused by repeated flooding. (AP / Wayne Parry Photo)

THERE IS NO SIMPLE SOLUTION

So what can be done? Building a sea embankment or embankment is one of the immediate solutions. This of course stops water getting in, but remember that the sea wall is sinking too, so it has to be extra large to be effective in the long term.

In urban areas, engineers can’t lift the ground easily: It can take decades as buildings and infrastructure are updated. There is no simple solution, and large-scale urban land subsidence is largely irreversible.

Several cities have found “solutions”. Tokyo, for example, succeeded in stopping land subsidence from around 1960 onwards thanks to stronger regulations on water pumping, but it could not eliminate the overall risk as parts of the city are below sea level and depend on embankments and pumps to be habitable.

Indonesia’s bold proposal to move its capital city may be the ultimate solution.

Increased urbanization especially in delta areas and freshwater demand means land subsidence will remain a pressing issue in the coming decades.

Addressing land subsidence is complementary to addressing climate-induced sea level rise and both need to be addressed. The combination of rising sea levels and sinking land will further endanger coastal cities.

Hear how changes in the oceans are causing sea levels to rise in this episode of The Climate Conversations:

Sally Brown is a scientist at Bournemouth University and Robert James Nicholls is professor of Climate Adaptation, University of East Anglia. This comment first appearance on The Conversation.

.



image source

Hundreds of Pacific Islands are getting bigger despite global warming | Instant News


New research says hundreds of islands in the Pacific are growing in land size, even as climate-related sea levels threaten the region.

Scientists at the University of Auckland found atolls in Pacific countries in the Marshall Islands and Kiribati, as well as the Maldives archipelago in the Indian Ocean, have grown by 8 percent in the past six decades despite rising sea levels.

They say their research can help climate-prone countries adapt to future global warming.

Scientists are using satellite images of the islands as well as field analysis to track these changes.

Coastal geomorphologist Dr Paul Kench said coral reef sediments were responsible for building the islands.

Dr Kench said in areas where coral reefs were healthy, enough sediment was produced to make the islands grow.

Historical aerial images show how the coastline of Jeh has changed over the decades.(Supplied)

“The majority of the islands in each of these countries have become larger or remain very similar in size,” he said.

“So, you know, one of the great things about this job is that the islands are actually quite physically dynamic.”

Healthy coral reefs are the key to growth

Coastal erosion due to rising sea levels is considered a major threat to many Pacific communities, with some witnessing coastlines receding.

Dr Kench said about 10 percent of the islands captured in the study were getting smaller in size.

Laguna Enewetak in the Marshall Islands with a small boat capsized on the shore.
Many of the islands in the Pacific are low-lying and at risk from rising sea levels.(ABC News: Greg Nelson)

He said a better understanding of which islands are growing and which are experiencing erosion could help Pacific countries adapt to climate change.

“That gives island nations the power to think about adaptation strategies, about where you focus on further development, and you will probably select islands that we can show are really growing in size,” he said.

Dr Kench said more work needs to be done to understand other factors affecting the growth or reduction of Pacific islands.

One of the concerns is the degradation of coral reefs due to global warming.

“Even though we can see healthy sites, and the sediment production that creates the islands is still happening, there should be some concern in locations where coral reef conditions are poor,” he said.

“So we are not suggesting here with any imagination that the island should not be worried.

“I think one of the messages from the work we’re doing is that island outcomes and prognosis will vary widely from site to site.”

.



image source

Projections for Sea Level Rise Exceed IPCC Estimates | Instant News


submitted a photo of Diamantino Rosa

By

Maritime Executive

10-05-2020 08:08:27

An international study led by Nanyang Technological University (NTU) in Singapore has found that global average sea level rise can exceed one meter at 2100 and five meters at 2300 if global targets on emissions are not achieved.

The study uses projections by more than 100 international experts for global average sea level changes in two climate scenarios – low and high emissions. In scenarios where global warming is limited to 2 degrees Celsius above pre-industrial levels, experts estimate a rise of 0.5 meters at 2100 and 0.5 to two meters at 2300. In high emission scenarios with 4.5 degrees Celsius warming, Experts estimated that the increase was greater than 0.6 to 1.3 meters in 2100 and 1.7 to 5.6 meters in 2300.

Sea level rise projections exceed previous estimates by the International Panel on Climate Change (IPCC).

“We know that the planet will see additional sea level rise in the future,” said co-author Dr. Andra Garner, Assistant Professor of Environmental Sciences at Rowan University in the US. “But there are striking differences in the number of sea level rise expert projects for low emissions compared to high emissions. This gives a lot of hope for the future as well as strong motivation to act now to avoid the more severe effects of sea level rise. “

This study is based on opinions informed by 106 sea level experts. The 106 experts who participated in the survey were chosen because they were one of the most active publishers of scientific sea-level studies (at least six papers published in peer-reviewed journals since 2014) were identified from leading publication databases.

Responding to open questions, climate change experts identified Greenland and Antarctica Ice Sheets as the biggest source of uncertainty. This ice sheet is an important indicator of climate change and a driver of sea level rise. Satellite-based measurements show the ice sheet is melting at high speed. However, experts also note that the magnitude and impact of sea level rise can be limited by successfully reducing emissions.

Professor Benjamin Horton, Acting Chairperson of the NTU Asian School of Environment, led the survey published in the Journal of the Partners of Nature, Climate and Atmospheric Sciences. Collaborative projects include researchers from the University of Hong Kong, Maynooth University (Ireland), Durham University (UK), Rowan University, Tufts University (US), and the Potsdam Institute for Climate Impact Research (Germany).

.



image source